This is a traditional pincer that is still played.
White's normal answers are at a, tenuki, at b and c.
Alex Weldon: I've been searching unsuccessfully for the continuation if White plays at c. Someone help me out?
The jump out at j was played in old Chinese games, but isn't a major variation in comtemporary go.
The white 'a' reply is a double kakari. is one way out of a double kakari.
is not at b because you're not supposed to attach to the weaker (pincered) stone[1]. Attaching to the pincered stone makes the pincer a bit superfluous.
could also be at
, but this is one possible joseki. White get's the left side, and black get's the top side - which is what black was hoping for with the pincer at
. - Fhayashi
Against this Black can still lean on the stronger stone with the outer attachment of
, building a wall in the direction facing the pincer.
After Black has a choice: a is peaceful, while b and c can lead to complications.
[1]
This piece of advice appears in some books, but is misleading. Charles